An inertial navigational system (INS) is a type of navigational system or a tracking system used, for example, on aircraft, vehicles, human being or other moving objects to obtain their location information. The working of an INS is based on the measurement of acceleration and rotation rate of a body that is to be tracked. A traditional INS utilizes accelerometers, gyroscopes, electronic compass and support electronics, such as a processor, in order to translate sensor data into motional changes. Navigational information such as velocity, orientation, and position can be determined from the sensor data by computers or other instrumentation.
A typical INS comprises a wireless inertial navigational device and a host device that is in communication with the inertial navigational device. The inertial navigational device can be carried by or transplanted by a user, for example carried by a human being or mounted in, a vehicle or other moving object. The host device can be carried by the INS user in a remote location and can display the location of the user. The inertial navigational device determines the position of the user using, in part, an electronic compass and can communicate this information to the host device, which can, then, display the location of the user.
Existing inertial navigational systems that utilize electronic compasses or other magnetic devices provide variations in location information of a user if the user's inertial navigational device is under the influence of static magnetic field variations. Thus, the position of an INS which incorporates the use of magnetic devices, such as electronic compasses, is only as good as the natural magnetic field accuracy in the area that the magnetic device is being used. If an area that a user is being tracked contains strong magnetic field (B-field) variations, then the accuracy of the INS can be greatly diminished. The B field, or magnetic field variations, can be caused by large magnets, large screen televisions, generators, large iron objects, and other devices that influence the surrounding natural magnetic field. The user can be completely unaware of these variations and can be subjected to unsafe tracking conditions, such as translating the location of the user to a position outside of the required positional resolution rendering the user lost.
For example, in an emergency medical or a security situation, it is essential for an Incident Scene Commander (ISC) to keep track of the First Responders at the scene of a crisis, for example a fire inside a building. Location data of the First Responders, each having an inertial navigational device, can be communicated to the ISC's host computer. The location information of the First Responder's position can then be displayed on the ISC's computer. In such situations, obtaining the precise location of the First Responders is very important. However, if there are large screen televisions, large magnets, generators, large iron objects or other magnetic devices in the building, the location of the First Responders displayed at the ICS's computer can be inaccurate and can lead to confusion and even fatal errors in the crisis management plan.
Thus, there exists a need for a method of obtaining improved location accuracy of an inertial navigational device by correcting real-time data generated at the inertial navigational device in the presence of strong magnetic field variations using magnetic field mapping.